Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 311547
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
847 AM PDT MON AUG 31 2015

.UPDATE...OTHER THAN SOME AREAS OF LOW CLOUDS AND FOG ALONG THE
COAST AND IN THE UMPQUA VALLEY, CLEAR AND COOL CONDITIONS DOMINATE
THE FORECAST AREA. WITH CALM WEATHER IN THE AREA, THE PREVIOUS
FORECAST IS RIGHT ON TRACK, SO NO CHANGES ARE NECESSARY THIS
MORNING. FOR MORE INFORMATION, SEE THE PREVIOUS DISCUSSION BELOW.


&&

.AVIATION...FOR THE 31/12Z TAF CYCLE...CLOUDS ALONG THE COAST
EASTWARD INTO THE UMPQUA BASIN AND SOUTHERN OREGON CASCADES WILL
CONTINUE PARTIAL TERRAIN OBSCURATIONS THIS MORNING. LOWER ELEVATIONS
AREAS ALONG AND NEAR THE COAST AND INTO THE UMPQUA BASIN WILL SEE
AREAS OF MVFR CIGS AND LOCAL IFR CIGS. OTHERWISE, VFR IS GENERALLY
EXPECTED ELSEWHERE. CONDITIONS ARE EXPECTED TO IMPROVE TO VFR AT ALL
LOCATIONS DURING THE MID TO LATE MORNING. MVFR/IFR CIGS IN STRATUS
WILL RETURN TO THE COAST THIS EVENING AND TONIGHT AND LOCAL MFR/IFR
CIGS ARE POSSIBLE LATE TONIGHT IN THE UMPQUA BASIN. /CC

&&

.MARINE...UPDATED 830 AM PDT MONDAY 31 AUGUST 2015...WEAK HIGH
PRESSURE WILL PERSIST OVER THE WATERS TODAY INTO TUESDAY, WITH WINDS
REMAINING LIGHT TO MODERATE AND SEAS DOMINATED BY A WESTERLY SWELL.
ANOTHER FRONT WILL MOVE OVER THE WATERS LATE TUESDAY BRINGING SOME
LIGHT RAIN SHOWERS.  SEAS MAY BECOME STEEP WEDNESDAY INTO WEDNESDAY
NIGHT AS NORTHWEST SWELL INCREASES OVER THE WATERS.   EXPECT
CONTINUED UNSETTLED CONDITIONS THROUGH FRIDAY. NORTH WINDS MAY
INCREASE LATE FRIDAY INTO THE WEEKEND. THIS MAY RESULT IN SMALL
CRAFT ADVISORY WINDS AND STEEP SEAS OVER THE WATERS. -BPN/CC

&&

.PREV DISCUSSION... /ISSUED 520 AM PDT MON AUG 31 2015/

DISCUSSION...31/00Z NAM/GFS IN.

THE LONG WAVE TROUGH THAT BROUGHT THE WINDS AND PRECIPITATION TO
THE AREA OVER THE PAST FEW DAYS HAS NOW MOVED OUT TO THE
EAST...AND WEAK TO MODERATE ZONAL FLOW ALOFT IS IN PLACE OVER THE
PACIFIC NORTHWEST. SOME LIGHT SHOWERS PERSIST...MOSTLY OVER THE
CASCADES...BUT THEY WILL DISSIPATE SOON.

THE MEDFORD CWA WILL REMAIN UNDER MODERATE ZONAL FLOW MONDAY INTO
TUESDAY MORNING WITH THE STORM TRACK TO THE NORTH OF THE AREA.
MONDAY WILL BE DRY AND HIGH TEMPERATURES WILL BE AROUND NORMAL
VALUES OVER MOST OF THE AREA. SISKIYOU COUNTY AND THE UMPQUA BASIN
WILL BE SLIGHTLY ABOVE NORMAL.

HOWEVER...THE MEDFORD CWA WILL CATCH THE WEAK SOUTHERN END OF
SYSTEMS MOVING ONSHORE. THE FIRST OF THESE WILL MOVE IN TUESDAY
AND IT WILL BRING A SLIGHT CHANCE OF LIGHT RAIN TO THE
COAST...COAST RANGE...AND UMPQUA BASIN. THE PRECIPITATION AND
CLOUD COVER WILL MAKE FOR A COOLER DAY OVER THOSE AREAS WITH HIGHS
NEAR NORMAL TO ABOUT 5 DEGREES BELOW NORMAL. HIGHS WILL BE NEAR
NORMAL VALUES OVER THE REST OF THE AREA.

ANOTHER LONG WAVE TROUGH WILL DIG SOUTH INTO THE PACIFIC NORTHWEST
TUESDAY NIGHT INTO WEDNESDAY. THIS WILL FORCE THE STORM TRACK
FARTHER SOUTH. THE INITIAL SURFACE FRONT WILL MOVE ONSHORE TUESDAY
NIGHT NIGHT INTO WEDNESDAY MORNING. WITH LITTLE UPPER LEVEL
SUPPORT IT WILL BE WEAK. THE NORTH COAST WILL ONCE AGAIN GET MOST
OF THE PRECIPITATION...WITH VERY LIGHT AMOUNTS FARTHER INLAND FROM
THE CASCADES WEST AND SISKIYOUS NORTH. UPPER KLAMATH COUNTY MAY
GET SOME MEASURABLE RAIN TOO. INLAND HIGH TEMPERATURES WILL COOL
DOWN AROUND TO AROUND 5 TO 10 DEGREES BELOW NORMAL.

THE LONG WAVE TROUGH WILL TRY TO KICK OUT TO THE EAST WEDNESDAY
AFTERNOON...BUT SHORT WAVES DIVING DOWN THE BACK SIDE OF THE
TROUGH WILL FORCE IT TO DIG AND RETROGRADE. THE MODELS DIFFER ON
THE EVOLUTION OF THIS TROUGH. THE 31/00Z GFS FINALLY MOVES IT OUT
TO THE EAST BY SATURDAY...WHILE THE 30/12Z EC IS ABOUT 12 TO 18
HOURS SLOWER. EITHER WAY...THURSDAY AND FRIDAY LOOK TO BE COOL
WITH INLAND HIGHS WILL BE 5 TO 15 DEGREES BELOW NORMAL. WOULD ALSO
EXPECT SOME SHOWERS WITH THIS PATTERN...BUT THE GFS SOLUTION IS
MOSTLY DRY DURING THIS INTERVAL. THE WETTER EC LOOKS LIKE THE
BETTER FORECAST DURING THIS STRETCH. THERE IS A SLIGHT CHANCE OR
CHANCE OF SHOWERS IN THE CURRENT FORECAST OVER PARTS OF THE
MEDFORD CWA...SO WILL NOT CHANGE AT THIS TIME. HOWEVER...POPS MAY
NEED TO BE UPPED AS THE EVENT APPROACHES.

THE OUTLOOK FOR SATURDAY IS MURKIER. IT MAY BE COOL AND SHOWERY
WITH A TROUGH OVERHEAD...OR COOL AND DRY WITH THE TROUGH TO THE
EAST...UNDER NORTHWEST FLOW ALOFT AND OFFSHORE LOW LEVEL FLOW.
SUNDAY LOOKS TO BE DRIER AND WARMER.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

BPN/CC/JRS


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